The present invention relates to a copy system and a copy method, and, for example, can be suitably applied to a storage system.
From the past, remote copy of copying data written in a logical volume of a storage apparatus set as a primary side (this is hereinafter referred to as the “primary storage apparatus”) to a logical volume of a storage apparatus set as a secondary side has been widely employed.
In remote copy, after setting a copy pair with a logical volume of the copy source in the primary storage apparatus as a primary volume, and a logical volume of the copy destination in the secondary storage apparatus as a secondary volume, all areas of the primary volume are copied to the secondary volume (this is hereinafter referred to as the “initial copy”). Subsequently, when new data is written in the primary volume, such data is transferred from the primary storage apparatus to the secondary storage apparatus synchronously or asynchronously with the writing of data so as to write this data in the same location as the primary volume in the secondary volume. According to this kind of remote copy, it is possible to mirror and retain data, and prevent the loss of data caused by disasters or the like.
Incidentally, Japanese Patent Laid-Open Publication No. 2005-141381 (Patent Document 1) and Japanese Patent Laid-Open Publication No. 2001-337939 (Patent Document 2) describe a remote copy method in a case when a secondary storage apparatus succeeds the operations of a primary storage apparatus for maintenance or other reasons, including the steps of managing the differential between the primary volume and the secondary volume with a differential bitmap, and, when resuming the operations of the primary storage apparatus, using this differential bitmap to copy only the differential from the secondary volume to the primary volume.
Further, Japanese Patent Laid-Open Publication No. 2006-268740 (Patent Document 3) describes a remote copy method, including the steps of creating a backup of a primary volume, copying such backup to a secondary volume, managing the update of the primary volume after the creation of a backup with a differential bitmap, copying the backup data to the secondary volume, and using a differential bitmap to copy only the differential from the primary volume to the secondary volume.